Yet another weird thing that Ryan and I say (quite a lot, actually) is "a best" as in "you are a best."
It started off as a grammar joke, but evolved into something meaningful (?). Using "the" seems so definitive. If you're the best, you're the absolute best. There can be no others, right? However, if you say "you're a best" then you're meaning to say that 'you're one of the best.' Not as absolute, but a decent compliment just the same. For us, it's an honorific. We don't say you're a best if you're not. Luckily, we know a lot of people who are A bests!
You can also expect to hear:
"you are a funniest!"
"you are a cute!"
"you are a ass!"